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Numerical Inequalities · Question 77 of 79

Question 77

HardOriginal question

Ravi is twice as old as his sister, and their ages add up to less than 45 years. His sister is at least 12. Which whole numbers can her age be?

Options for question 77

Show the answer and explanation
CorrectNot quiteAnswer D

Correct answer: D

Explanation

  1. With her age ss, Ravi is 2s2s: s+2s<45s + 2s < 45, so s<15s < 15.

  2. With s≥12s \ge 12: 12≤s<1512 \le s < 15, that is 12, 13 or 14.

Worth noting

15 is left out: 15+30=4515 + 30 = 45 is not less than 45.

Concept
Two conditions together
Typical time
120 s
Your time
—
The rule this testsInequalities from situations
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